California is not as progressive as you might hope. The cities are full of progressives, but outside the cities is very conservative. You have to be fairly moderate to win statewide office.
Newsom was a reaction to Trump, but sort of an aberration. More than half of our governors have been Republicans, including Regan, who went on be President and a paragon of the GOP.
Since the 80s 14 out of 30 years has been Republicans, and Jerry Brown was 10 of the remaining 16 years, and he's pretty moderate as far as Democrats go.
I mean, yes. Feinstein is better than the alternative in the General. The Primaries are the way to get rid of her, I can't believe no one has booted her out yet.
You don't seem to understand the California Jungle/Blanket primary system... All candidates from any/all parties run against each other in the primary, and the top two are the contenders for the general election. Recently this has led to two Democrats always being facing each other in the general election.
The most recent general election was Dem vs Dem (due to the unique way that CA primaries work). Feinstein still won a strong majority of the statewide vote. :|